Digital imaging systems, such as those employed for converting still color photographic film (e.g. 35 mm) images into digital format for storage in a digital database and subsequent playback, as by way of a color television monitor, customarily encode the output of an electronic film scanning device, such as a digital color camera, to some prescribed resolution and store the encoded image in an associated database as a respective image file. When it is desired to display a particular stored image, the contents of the respective addresses of the database in which the digitized image has been stored are read out and coupled to display driver circuitry for energizing corresponding pixels on the TV monitor.
Because each frame of a typical roll of 35 mm film has different horizontal and vertical frame dimensions, for example a dimension of 36 mm in the horizontal direction, parallel to the lengthwise direction of the film, and a dimension of 24 mm in the vertical direction, orthogonal to the lengthwise direction of the film (a horizontal:vertical aspect ratio of 3:2), a photographer often rotates the camera ninety degrees about the lens axis in order to capture a subject in what is conventionally referred to as a `vertical` orientation. `horizontally shot` image, then, when a `vertically shot` image is displayed, it will be rotated unless the recording and playback system has been designed to accommodate vertical images.
One conventional approach to handle the problem, similar to that described in the Ohta U.S. Pat. No. 4,641,198, is to rotate those film frames which contain vertical images by ninety degrees before scanning and to fill in the left and right sides of the image with a uniform `border` color (e.g. black). Although this scanning method will provide the proper orientation of the displayed image, it suffers from two drawbacks. First, the actual scanning mechanism must be modified to effect an orthogonal scan of a vertical image. This is traditionally accomplished by physically reorienting the film by ninety degrees and changing the lens magnification of the scanning device by an amount related to the frame aspect ratio. Secondly, since side borders, which contain no useful information in terms of the captured image, are also recorded, some of the information storage capacity of the recording medium is wasted. A second solution to the problem is to rotate the display device, which is obviously impractical in many applications.
A third solution is to allow for different image orientations to be stored, together with digital control data indicating the orientations of the images, and to use an image playback device designed to read the orientation control data to properly orient the images on playback. Some prior art computer image file formats, for example the Tag Image File Format (TIFF), Revision 5.0, developed jointly by Aldus Corporation, Seattle, Wash., and Microsoft Corporation, Redmond, Wash., and described in "An Aldus/Microsoft Technical Memorandum:8/8/88," include the provision for an optical "tag" which can be used to indicate the orientation of the image. Page 25 of the above-mentioned TIFF document, described the TIFF "Orientation" tag, which can have eight different values indicating whether the zeroth row and zeroth column of the pixel data matrix represents the top and left, the top and right, the bottom and right, bottom and left, left and top, right and top, right and bottom, of left and bottom of the visual image. However, the above-mentioned memo further states that this field is recommended for private (non-interchange) use only. The default condition, where the zeroth row represents the visual top of the image, and zeroth column of the pixel data matrix represents the visual left hand side of the image, is recommended for all "non-private" applications, including those involving importing and printing. Thus, the TIFF orientation tag is never used to re-orient for display images which have been stored in different orientations in an image database.
In addition to the problem of different image orientations, captured images may have different aspect ratios. For example, dedicated use panoramic cameras, such as the Kodak Stretch (Trademark) camera, have an aspect ratio of 3:1, which is considerably wider than the above-referenced 3:2 aspect ratio of conventional 35 mm cameras. Other camera types, such as those which employ 126 type film also have aspect ratios other than 3:2.
In accordance with the invention described in co-pending patent application Ser. No. 022,603, filed Sep. 14, 1990, entitled "Mechanism for Controlling Presentation of Displayed Image, " by K. Parulski et al, assigned to the assignee of the present application, and the disclosure of which is incorporated herein, rather than employ a complex and costly hardware arrangement that physically rotates the film scanner relative to the film for non-upright horizontal images (e.g. vertical images), each image is digitized and stored on a digital data storage medium, such as a `write once` compact disc, in the same orientation as it is captured on film. In addition, a `presentation` header is annexed to each image file. This header, which is prepared by a photofinishing minilab operator who views the output of the film scanner, is formatted to contain a set of orientation and aspect ratio codes that indicate how the image has been captured on film and, correspondingly, how it is stored on the disc. Subsequently, when the disc is inserted into a playback device, such as a CD player, which drives an output display such as a color TV monitor, the playback device decode presentation control file information, and controls the presentation of the image such that the image is displayed in an upright orientation and at the correct aspect ratio for the display.
FIG. 1 diagrammatically illustrates a digital image system for a photoprocessing mini-lab, in which photographic images, such as a set of twenty-four or thirty-six 36 mm.times.24 mm image frames of a 35 mm film strip 10, are scanned by a high resolution opto-electronic film scanner 12, such as a commercially available Eikonix 1435 scanner. High resolution scanner 12 outputs digitally encoded data representative of the response of each of the pixels of its high resolution imaging sensor pixel array (e.g. a 3072.times.2048 pixel matrix). Typically, the color response of each pixel may be resolved into eight bits per color, so that, for a three color sensor array, the response of each sensor pixel is encoded into twenty-four bits. This digitally encoded data, or `digitized` image, is coupled in the form of an imaging pixel array-representative bit map to an attendant photofinishing workstation 14, which contains a frame store and image processing application software through which the digitized image may be processed (e.g. enlarged, cropped, subjected to a scene balance correction mechanism, etc.) to achieve a desired base image appearance. Once the base image has been prepared, it is to be written onto a transportable medium, such as a write once optical compact disc 15, using an optical compact disc recorder 16, for subsequent playback by a disc player 20, which allows the image to be displayed, for example, on a television set 22, or printed as a finished color print, as by way of a high resolution thermal color printer 24.
Advantageously, the imaging system described in the above referenced co-pending application takes advantage of the imaging mechanism described in U.S. Pat. No. 4,969,204, entitled "Hybrid Residual-Based Hierarchical Storage and Display Method for High Resolution Digital Images in a Multiuse Environment, " by Paul W. Melynchuck et al, assigned to the assignee of the present application and the disclosure of which is herein incorporated. Pursuant to that system, each high resolution captured image is stored as a respective image data file containing a low, or base, resolution image bit map file and a plurality of higher resolution residual images associated with respectively increasing degrees of image resolution. By iteratively combining these higher resolution residual images with the base resolution image, successively increased resolution images may be recovered from the base resolution image for application to a high resolution reproduction device.
In order to accommodate data values representative of a scanned 36 mm-by-24 mm image frame of a 35 mm film strip, an original high resolution (3K.times.2K) image may be decimated into an image data file made up of a base resolution digitized image of 768.times.512 pixels of luminance information (and an associated 384.times.256 pixels of two records of chrominance information, set of residual image files). Pursuant to a preferred image processing operator, the base resolution file is formatted to consist of luminance and chrominance information interleaved in the following manner. Since there are twice as many lines of luminance as chrominance, one line of chrominance is interleaved with two lines of luminance, such that the resulting file has the structure of 768 pixels of luminance, 384 pixels of chrominance record one, 384 pixels of chrominance record two, and 768 pixels of luminance.
For the above-referenced file, the total memory capacity required for the base image is 0.5625 megabytes, so that the frame store and its associated read/write circuitry (including the need for separate line and pixel clocks) within the playback device becomes a significant cost item in the overall architecture of the CD player.